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STRUCTURES TEAM

Specification Guidelines for Precast/Prestressed Concrete Bridge Products

Index
Item/Specification/Standard
Notes/Comments
1 MATERIALS  
  Specified properties of all materials shall be verified by appropriate AASHTO or ASTM standard tests either performed by the material supplier or the precast concrete plant.

In order to establish evidence of proper manufacture and conformance with plant standards and project specifications, a system of records shall be maintained to provide full information on material tests, mix designs, concrete tests, and any other necessary information.

For control of concrete, testing of specimens, and design and control of concrete mixes, each precast concrete plant shall be equipped with adequate testing equipment and staffed with personnel trained in its use.

If the plant has contracted for quality control to be performed by an outside independent laboratory, the laboratory shall be accredited by the Cement and Concrete Reference Laboratory of the National Institute of Standards and Technology (National Voluntary Laboratory Accreditation Program). The laboratory shall conform to the requirements of ASTM E329 and the plant or independent laboratory shall meet the concrete inspection and testing section requirements of ASTM C1077.

 
  Suppliers of materials shall be required to furnish certified test reports for cement, aggregates, admixtures, curing materials, reinforcing and prestressing steel, and hardware materials, indicating that these materials comply with the applicable AASHTO and ASTM standards, project specifications and plant standards.  
1.1 Cement  
  Cement shall conform to AASHTO M85.

If mill certificates are not supplied, representative testing of each shipment of cement is required before use. The mill certificate shall contain the alkali content in percent expressed as Na2O equivalent. Mill certificates or test reports of cement shall be kept on file in the plant for at least 5 years after use.

Mill test reports should be reviewed for changes from previous reports. Lower concrete strength should be expected from: lower cube strength; lower C3S; lower fineness; higher % retained on No. 325 sieve (45 mm); and higher loss on ignition. Increase in total alkali may reduce concrete strength gain after 7 days and impair the strength-producing efficiency of water-reducing admixtures. Variation in the color of gray cement may in part be traced to a variable Fe2O3 content (a 2% variation in Fe203 being significant).
1.1.1 Type  
  Type shall be as specified in the contract documents. If not specified Types I, II, III, IV, or V may be used.

Each shipment shall be referenced to a certified mill test report, indicating compliance with the specified type and compliance with AASHTO M85. Test reports shall be on file with the producer.

 
1.1.2 Alkali Content  
  If the aggregates used result in mortar bar expansion greater than 0.20% at an age of 16 days when tested in accordance with AASHTO T303, the equivalent alkali content (Na2O + 0.658K2O) of the cement shall not exceed 0.60%. If the AASHTO T303 test results in 16 day mortar bar expansion greater than 0.10% but less than 0.20% the equivalent alkali content of the cement shall not exceed 0.60% unless additional testing or examinations in accordance with ASTM C295 and ASTM C856 indicate that reactive constituents are negligible.  
1.1.3 Fineness  
  Fineness of Type III Portland Cement shall not exceed 5600 cm2/gm determined in accordance with AASHTO Test Method T153.  
1.1.4 Blended Hydraulic Cement  
  Blended hydraulic cement shall conform to AASHTO M240. AASHTO M85 (ASTM C150) -- Standard Specification for Portland Cement 
AASHTO M240 (ASTM C595) -- Blended Hydraulic Cement 
AASHTO T106 (ASTM C109) -- Compressive Strength of Hydraulic Cement Mortar 
AASHTO T127 (ASTM C183) -- Sampling and Amount of Testing of Hydraulic Cement
AASHTO T131 (ASTM C191) -- Time of Setting of Hydraulic Cement by Vicat Needle 
AASHTO T185 (ASTM C359) -- Early Stiffening of Portland Cement (Mortar Method) 
                                AASHTO T303 -- Rapid Identification of Alkali Silica Reaction Products in Concrete AASHTO T153 (ASTM C204) -- Standard Test Method for Fineness of 
Hydraulic Cement by Air Permeability Apparatus
ASTM C295 -- Petrographic Examination of Aggregates for Concrete 
ASTM C856 -- Petrographic Examination of Hardened Concrete
1.2 Aggregates  
  Sieve analysis, in accordance with AASHTO T27, shall be conducted on samples taken from the initial shipment received at the plant. Specific gravity, absorption, and petrographic analysis tests performed within the past 5 years shall be obtained from the supplier prior to the time of first usage or when a new lift or horizon in a quarry is utilized or there appears to be a change in quality of the aggregate.

Tests for deleterious substances and organic impurities shall be done at the start of a new aggregate supply and annually thereafter, unless problems are encountered requiring more frequent testing.

 
1.2.1 Alkali-Silica Reaction  
  Evaluation of aggregates for potential alkali-silica or alkali-carbonate reactions (excessive expansion, cracking, or popouts in concrete) shall be based on at least 15 years of exposure to moist conditions of structures made with the aggregate in question, if available, or petrographic examination (ASTM C295) to characterize aggregates and determine the presence of potentially reactive components.   
1.2.2 Petrography  
  If an aggregate is found to be susceptible to alkali-silica reaction using ASTM C295, it shall be evaluated further using ASTM C1260 and CSA A23.2-14A. Aggregates which exhibit ASTM C1260 mean mortar bar expansion at 14 days greater than 0.10 percent shall be considered potentially reactive. Aggregates further evaluated by CSA A23.2-14A that exhibit mean concrete prism expansion at one year greater than 0.04 percent shall be considered potentially reactive. Aggregate sources exhibiting expansions no more than 0.04 percent and demonstrating no prior evidence of reactivity in the field shall be considered non-reactive. Reliance shall not be placed on results of only one kind of test in any evaluation.

If an aggregate is judged to be susceptible to alkali-carbonate reaction using ASTM C295, it shall be evaluated further for alkali-carbonate reaction in accordance with ASTM C586 or ASTM C1105.

 
1.3 Coarse Aggregate  
  Coarse aggregates, other than lightweight aggregates, shall conform to the requirements of AASHTO M80.

The maximum size of coarse aggregate shall not exceed:

1. One third of the minimum section thickness.

2. Three-fourths of the minimum clear depth of cover.

3. Two-thirds of the spacing between individual reinforcing bars or bundles of bars or pretensioning tendons or post-tensioning ducts.

Coarse aggregates shall be obtained from sources from which representative samples have been subjected to all tests prescribed in the governing specifications.

 
1.3.1 Gradation  
  A sieve analysis (AASHTO T27) and unit weight test (ASTM C29) shall be conducted in the plant with test samples taken at any point between stockpile and batching hopper for aggregate being used. Such tests shall be carried out for each aggregate type and size in use at least once every week or for each 1,000 tons where usage in a one-week period exceeds such volume.  
1.3.2 Moisture Content  
     
1.4 Fine Aggregate  
  Fine aggregates shall comply with AASHTO M6 or applicable specified requirements. Variations in fineness modulus of fine aggregates shall not exceed _0.20 from the value used for the mix design and the amount retained on any two consecutive sieves shall not change by more than 10 percent by weight of the total fine aggregate sample.  
1.4.1 Materials  
  Fine aggregates for concrete mixes, other than lightweight aggregates, shall consist of high quality natural sand or sand manufactured from coarse aggregate.  
1.4.2 Gradation  
  A sieve analysis (AASHTO T27) and unit weight test (ASTM C29) shall be conducted in the plant with test samples taken at any point between stockpile and batching hopper for aggregate being used. Such tests shall be carried out for each aggregate type and size in use at least once every week or for each 500 tons where usage in a one-week period exceeds such volume.  
1.4.3 Moisture Content  
     
1.5 Lightweight Aggregate  
  Tests for gradation, unit weight and impurities shall be made in accordance with requirements of AASHTO M195.  
1.5.1 Materials  
  Lightweight aggregates shall conform to the requirements of AASHTO M195 (ASTM C330).   
1.5.2 Specific Gravity  
  The specific gravity of lightweight aggregate shall be determined in accordance with procedures described in ACI 211.2, Appendix A C Pycnometer Method. The oven-dry loose unit weight (ASTM C29) of the lightweight aggregate shall be determined. A maximum 10 percent change in unit weight of successive shipments from a sample submitted for acceptance tests is allowed.  
1.5.3 Moisture Content  
 
AASHTO M80 -- Coarse Aggregate for Portland Cement Concrete
ASTM C33 -- Standard Specification for Concrete Aggregates
AASHTO M6 -- Fine Aggregate for Portland Cement Concrete
AASHTO M43 -- Sizes of Aggregate for Road and Bridge Construction
AASHTO M195 (ASTM C330) --  Lightweight Aggregates for Structural Concrete

AASHTO T2 (ASTM D75)AASHTO T11 (ASTM C117) -- Sampling of AggregatesMaterials Finer Than 75-?m (No. 200) Sieve in 
Mineral Aggregates by Washing Unit Weight and Voids in Aggregate
AASHTO T19 (ASTM C29) -- Organic Impurities in Fine Aggregates for Concrete
AASHTO T21 (ASTM C40) -- Sieve Analysis of Fine and Coarse Aggregate
AASHTO T27 (ASTM C136) -- Specific Gravity and Absorption of Fine Aggregate
AASHTO T84 (ASTM C128) -- Specific Gravity and Absorption of Coarse Aggregate
AASHTO T85 (ASTM C127) -- Total Moisture Content of Aggregate by Drying
AASHTO T255 (ASTM C566) -- Accelerated Detection of Potentially Deleterious 
AASHTO T303 -- Expansion of Mortar Bars Due to Alkali-Silica Reaction
Petrographic Examination of Aggregates for Concrete
Potential Alkali Reactivity of Carbonate Rocks for 
ASTM C295 -- Concrete Aggregates (Rock Cylinder Method)
ASTM C586 -- Length Change of Concrete Due To Alkali-Carbonate Rock Reaction
ASTM C1105 -- Potential Alkali Reactivity of Aggregates (Mortar Bar Method)
ASTM C1260 -- Methods of Test for Concrete
CSA A23.2

1.6 Water  
  Water shall be free from deleterious matter that may interfere with the setting time or strength of the concrete.

Water, either potable or non-potable, shall be free from injurious amounts of oils, acids, alkalis, salts, organic materials, chloride ions or other substances that may be deleterious to concrete or steel.

Water shall not exceed the maximum concentration limits given in Table 1.6.

Water shall be potable or chemically analyzed when a private well or non-potable water is used in the concrete mix. Except for water from a municipal supply, an analysis of the water shall be on file at the plant, updated annually, and clearly related to the water in use. Seawater shall not be used.

Mortar cubes made in accordance with AASHTO T106 using nonpotable or questionable mixing water shall have 7-day strengths equal to at least 90 percent of the strengths of companion specimens made with potable or distilled water. Time of set (AASHTO T131) for mortar made with questionable water may vary from one hour earlier to 1-1/2 hours later than the control sample made with potable or distilled water. Water resulting in greater variations shall not be used.

Excessive impurities may cause efflorescence, staining, increased volume change and reduce durability. Therefore, limits should be set on chlorides, sulfates, alkalis and solids in the mixing water. Some impurities may have little effect on strength and setting time, yet they can adversely affect durability and other properties. The chloride ion content should be limited to a level well below the recommended maximum, if practical. Chloride ions contained in the aggregates and in admixtures should be considered in evaluating the acceptability of total chloride ion content of mixing water.
Table 1.6
 
1.7 Mineral Admixtures  
  Mineral admixtures or pozzolans meeting AASHTO M295 or ASTM C1240 may be added for additional workability, increased strength and reduced permeability and efflorescence. If a HRWR is used with silica fume, ensure that the admixture to be used is compatible with that already in the silica fume if any. The amount of silica fume or metakaolin in concrete shall not exceed 10 percent by weightof the portland cement unless evidence is available indicating that the concrete produced with a larger amount will have satisfactory strength, durability, and volume stability.  
1.7.1 Fly Ash  
  Fly ash or other pozzolans used as admixtures shall conform to AASHTO M295  
1.7.2 Silica Fume  
  Silica fume shall conform to ASTM C1240.  
1.7.3 Blast Furnace Slag  
     
1.7.4 Metakaolin  
  Metakaolin shall conform to ASTM C618 Class N requirements. AASHTO M295 (ASTM C618) - Coal Fly Ash and Raw or Calcinated Natural Pozzolan for Use as a Mineral Admixture in Concrete
AASHTO M302 (ASTM C989) - Ground Granulated Blast-Furnace Slag for Use in Concrete and Mortars
AASHTO M307 - Microsilica for Use in Concrete and Mortar
ASTM C311 - Sampling and Testing Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland Cement Concrete
ASTM C1240 - Silica Fume for Use as a Mineral Admixture in Hydraulic-Cement Concrete, Mortar, and Grout
1.8 Chemical Admixtures  
  If a satisfactory history of admixture performance with the specific concrete materials to be used in a project is not available, a trial mixture program with those materials, particularly the cement, shall be conducted. The trial mixture program shall demonstrate satisfactory performance of the admixture relative to slump, workability, air content, finishability and strength under the conditions of use, particularly with respect to temperature and humidity. Admixtures shall be carefully checked for compatibility with the cement or other admixtures used to ensure that each performs as required without affecting the performance of the other admixtures. Admixture supplier's recommendations shall be observed subject to plant checking and experience. The affect of variations in dosage and the sequence of charging the admixtures into the mixer shall be determined from the recommendations of the admixture supplier or by trial mixes. All types of admixtures used should be materials of standard manufacturing having well established records of tests to confirm their properties. Expected performance of a given brand, class, or type of admixture may be projected from one or more of the following sources:

1. Results from jobs which have used the admixture under good technical control, preferably using the same materials and under conditions similar to those to be expected.

2. Technical literature and information from the manufacturer of the admixture.

3. Laboratory tests made to evaluate the admixture.

Trial mixtures can be made at midrange slump and air contents expected or specified for the project. The cement content or water/cement ratio should be that required for the specified design strength and durability requirements for the job. Trial mixtures also can be made with a range of cement contents, water/cement ratios, slumps or other properties to bracket the project requirements. In this manner, the optimum mixture proportions can be selected and the required results achieved.

Various results can be expected with a given admixture due to differences in dosage, cement composition and fineness, cement content, aggregate size and gradation, the presence or other admixtures, addition sequence, changes in water/cement ratio and weather conditions from day to day.

Differences in setting times and early strength development also can be expected with different types and sources of cement as well as concrete and ambient temperatures.

  The manufacturer of the admixture shall certify that individual lots meet the appropriate AASHTO and ASTM requirements. All relevant admixture information with respect to performance, dosages, and application methods and limitations shall be on file at the plant. Other admixtures shall conform to the requirements of ASTM C494, Types A, B, D, F, and G, or ASTM C1017. The supplier shall certify these admixtures do not contain calcium chloride. 

Laboratory test reports submitted by the supplier of chemical admixtures shall include information on the chloride ion content and alkali content expressed as Na2O equivalent. Test reports are not required for air-entraining admixtures used at dosages less than 2 fl oz per 100 lb (130 ml per 100 kg) of cement or nonchloride chemical admixtures used at maximum dosages less than 5 fl oz per 100 lb (325 ml per 100 kg). Both the chloride ion and total alkali content of the admixture are to be expressed in percent by mass of cement for a stated or typical dosage of the admixture, generally in fluid ounces per 100 lb of cement or (milliliters per 100 kg).

 
  Calcium chloride or admixtures containing chloride ions (Cl-1) from other than impurities from admixture ingredients shall not be used in prestressed concrete, as their use will produce deleterious concentrations of chloride ions in the mixing water and cause corrosion.  
1.8.1 Air Entraining  
  Air entraining admixtures shall conform to the requirements of ASTM C260. The use of air entrainment is recommended to enhance durability when concrete will be subjected to freezing and thawing when wet.
1.8.2 Water Reducing  
  Water reducing, retarding or accelerating admixtures shall conform to the requirements of ASTM C494.  
1.8.3 Retarding  
     
1.8.4 WR & Retarding  
     
1.8.5 HRWR  
  High-range water-reducing admixtures (HRWR) or (superplasticizers) shall conform to the requirements of ASTM C494 Type F or G.  
1.8.6 HRWR & Retarding  
 
AASHTO M194 (ASTM C494) -- Chemical Admixtures for Concrete
ASHTO M154 (ASTM C260) -- Air-Entraining Admixtures for Concrete
1.9 Reinforcement  
  Plant testing of reinforcing steel, welded wire reinforcements, or prestressing materials shall not be required if mill certificates and coating reports are supplied. Mill certificates for reinforcing steel, welded-wire reinforcement, and prestressing materials in stock or in use shall be required and indicate that the material meets the requirements of applicable AASHTO and ASTM specifications.

Certificates shall be obtained for each size and shipment and for each grade of steel. 

Mill certificates for all reinforcing materials shall be kept on file at the plant for at least five years after use. Incoming steel, wire, and strand shall be examined for damage, excessive scaling, or pitting. 

 
1.10 Steel Reinforcement  
  Steel reinforcing bars shall be deformed bars of the designated types of steel, sizes and grades and shall conform to the applicable specifications as shown on the production drawings.  
  When it is required to restrict the range in the chemical composition of steel to provide satisfactory weldability, the supplier shall certify conformance with these supplemental requirements in writing.

In lieu of mill certificates, reinforcing steel shall be tested for its physical and chemical properties in accordance with ASTM A370 to verify conformance with the applicable specifications.

 
  It shall be permissible to substitute:
  • a metric size bar of Grade 300 for the corresponding inch-pound size bar of Grade 40;
  • a metric bar of Grade 350 for the corresponding inch-pound size bar of Grade 60;
  • and a metric size bar of Grade 520 for the corresponding inch-pound size bar of Grade 75.
 
  Reinforcement with rust, seams, surface irregularities, or mill scale shall be considered as satisfactory, provided the minimum nominal dimensions, including minimum average height of deformations, and nominal weight of a hand-wire-brush test specimen are not less than the applicable ASTM specification requirements.  
1.10.1 Galvanized  
  Zinc-coated (galvanized) reinforcement shall conform to ASTM A767/A767M and be chromate treated. Where galvanizing of reinforcing bars is required, galvanizing is usually performed after fabrication. The ASTM A767/A767M specification prescribes minimum finished bend diameters for bars that are fabricated before galvanizing. Smaller finished bend diameters are permitted if the bars are stress-relieved. The ASTM A767/A767M specification has two classes of zinc coating weights. Class II 2.0 oz/ft2 (610g/m2) is normally specified for precast concrete units.
1.10.2 Epoxy Coated  
  Epoxy-coated reinforcement shall conform to ASTM A775/A775M or A934/A934M. Any plant supplying epoxy-coated reinforcement shall be a participant in the CRSI Voluntary Certification Program for Fusion-Bonded Epoxy Coating Applicator Plants. Fading of the epoxy coating color shall not be cause for rejection of epoxy coated reinforcing bars. When epoxy-coated reinforcing bars are exposed to sunlight over a period of time, fading of the color of some epoxy coatings may occur. Since the discoloration does not harm the coating nor affect its corrosion protection properties, such fading should not be the cause for rejection of the coated bars. 
1.10.3 Welded Wire Fabric  
  Welded wire reinforcement shall conform to the following applicable specifications:
  • Plain Wire ASTM A82
  • Deformed Wire ASTM A496
  • Welded Plain Wire Reinforcement ASTM A185
  • Welded Deformed Wire Reinforcement ASTM A497
 
  The in-plant review and monitoring of welded-wire reinforcement shall include a periodic inspection as the material is received to confirm that the styles conform to the required size and spacing specified. Spacing of the wires shall be within 1/4 inch (6 mm) of the desired spacing, and the resistance welds at intersections of wires shall have not more than 1 percent broken welds. Additionally, if specific finish requirements are specified, such as galvanizing or epoxy coating, this shall be confirmed at the point of delivery.

Galvanized welded wire reinforcement shall be made from zinc-coated (galvanized) carbon steel wire conforming to ASTM A641; or be hot-dipped galvanized and be chromate treated; or be allowed to weather. Epoxy-coated welded wire reinforcement shall conform to ASTM A884/A884M, Class A. All damaged areas of epoxy coating shall be repaired (touched-up) with epoxypatching material.

Welded wire reinforcement mesh spacing and wire sizes (gages) shall be shown on the production drawings. 

AASHTO M31 (ASTM A615) - Deformed and Plain Billet-Steel Bars for Concrete Reinforcement
AASHTO M32 (ASTM A82) - Plain Steel Wire for Concrete Reinforcement
AASHTO M54 (ASTM A184) - Fabricated Deformed Steel Bar Mats for Concrete Reinforcement
AASHTO M55 (ASTM A185) - Plain Steel Welded Wire Fabric for Concrete Reinforcement
AASHTO M221 (ASTM A497) - Deformed Steel Welded Wire Fabric for Concrete Reinforcement
AASHTO M225 (ASTM A496) - Deformed Steel Wire for Concrete Reinforcement
AASHTO M284 (ASTM D3963) - Epoxy Coated Reinforcing Bars
ASTM A706 - Specification for Low-Alloy Steel Deformed and Plain Bars for Concrete Reinforcement
 
1.11 Prestressing Strand  
  Strand materials for prestressing shall consist of:
a. uncoated, low relaxation wire strand conforming to AASHTO M203, Grade 270 1860,
b. uncoated, stress relieved (normal relaxation) strand, conforming to AASHTO M203, Grade 270 1860.
 
  Mill certificates from suppliers shall be on file at plant offices for tendon materials in current use. Certificates shall be obtained and kept on file for each ten reels or coils of prestressing strand or wire in each size, and for each heat or at least for each shipment if less than ten reels or coils.

The stress-strain curve of the prestressing steel shall be on record. Stress-strain curves shall be for material tested from heats used to produce reel packs and shall be referenced to those reel packs. Average, typical or generic curves are not acceptable.

The capability of the strand to properly develop bond shall either be substantiated by certification from the strand supplier or by testing.

 
  A light bond coating of tight surface rust on prestressing tendons is permissible, provided strand surface shows no pits visible to the unaided eye after rust is removed with a non-metallic pad. Due to bond development required of concrete to prestressing strand, bars, or wires, the surface condition of tendons is critical to prestressed concrete. The presence of a light rust on a strand has proven to be an enhancement to bond over bright strand and therefore should not be a deterrent to the use of the strand. A pit visible to the unaided eye, when examined as described in AEvaluation of Degree of Rusting on Prestressed Concrete Strand@, Sason, Augusto S., PCI Journal, May-June 1992, V.37, No. 3 pp. 25-30 is cause for rejection. A pit of this magnitude is a stress raiser and greatly reduces the capacity of the strand to withstand repeated or fatigue loading. In many cases, a heavily rusted strand with relatively large pits will still test to an ultimate strength greater than specification requirements. However, it will not meet the fatigue test requirements.
 
AASHTO M203 (ASTM A416) -- Uncoated Seven-Wire Steel Strand for Concrete Reinforcement
AASHTO M204 (ASTM A421) -- Uncoated Stress-Relieved Steel Wire for Prestressed Concrete
1.12 Pre-Tensioning  
  Strand chucks for pre-tensioning shall be capable of anchoring the strand without slippage after seating. Length of grips and configuration of serrations shall be such as to ensure against strand failure within the vise jaws at stresses less than 95 percent of strand ultimate strength. Steel casings for strand vises shall be verified by the manufacturer as capable of holding at least 100 percent of the ultimate strength of the strand.  
  Devices used to deflect the strand to the required position shall be designed to minimize friction to the level consistent with the tolerances for strand tensioning. Strand shall be able to move freely over, under, or through the device. Harped strands must be held in position by devices capable of supporting the load imparted from the tensioned strand without excessive deformation. Excessive friction in such devices can cause the strand tension to vary over the length of the bed. If a strand becomes Apinched@ or otherwise caught in the device, strand breakage can occur.

Strand restraining devices should be designed for an appropriate factor of safety.

1.13 Post-Tensioning  
     
1.13.1 Bars  
 
AASHTO M275 (ASTM A772)
Uncoated High-Strength Steel Bar for Prestressing Concrete
1.13.2 Anchors  
  A tendon anchorage for post-tensioning shall meet the following requirements:
1. An anchorage for bonded tendons tested in an unbonded state shall develop 95 percent of the actual ultimate strength of the prestressing steel, without exceeding anticipated set attime of anchorage. An anchorage which develop less than 100 percent of the minimum specified ultimate strength shall be used only where the bond length provided is equal to or greater than the bond length required to develop 100 percent of the minimum specified ultimate strength of the tendon. The required bond length between the anchorage and the zonewhere the full prestressing force is required under service and ultimate loads shall be sufficient to develop the specified ultimate strength of the prestressing steel. Determine the bond length by testing a full-sized tendon. If in the unbonded state the anchorage develops 100 percent of the minimum specified strength it need not be tested in the bonded state.

2. An anchorage for unbonded tendons shall develop 95 percent of the minimum specified ultimate strength of the prestressing steel with an amount of permanent deformation that will not decrease the expected ultimate strength of the assembly.

3. The minimum elongation of a strand under load in an anchorage assembly tested in the unbonded state shall be not less than 2 percent when measured in a gauge length of 10-ft. (3 m).

Anchorage castings shall be nonporous and free of sand, blow-holes, voids and other defects. For a wedge type anchorage, the wedge grippers shall be designed to preclude premature failure of the prestressing steel due to notch or pinching effects under static test load conditions to determine yield strength, ultimate strength and elongation of the tendon.

An anchorage of any type may be used provided the basic requirements noted herein are demonstrated by an acceptable test program.

 
1.13.3 Duct  
  Sheathing for bonded post-tensioned tendons shall be strong enough to retain its shape, resist unrepairable damage during production, and prevent the entrance of cement paste or water from the concrete. Sheathing material left in place shall not cause harmful electrolytic action or deteriorate. The inside diameter shall be at least 1/4 in. (6 mm) larger than the nominal diameter of single wire, bar or strand tendons; or in the case of multiple wire, bar or strand tendons, the inside cross-sectional area of the sheath shall be at least twice the net area of the prestressing steel. Sheaths shall be capable of transmitting forces from the grout to the surrounding concrete. Sheaths shall have grout holes or vents at each end and at all high points except where the degree of tendon curvature is small and the tendon is relatively level. The void in the concrete in which the tendon is to be located may also be formed with inflatable and removable tubes. the tendon is subsequently pulled through and no additional sheathing is required.
  Sheathing for unbonded tendons (monostrand post-tensioning system) shall be polypropylene, high-density polyethylene or other plastic which is not reactive with concrete, coating or steel. The material shall be waterproof and have sufficient strength and durability to resist damage and deterioration during fabrication, transport, storage, installation, concreting and tensioning. The sheath shall have a coefficient of friction with the strand of less than 0.05. Tendon covering shall be continuous over the unbonded length of the tendon and shall prevent the intrusion of water or cement paste and the loss of the coating material during concrete placement. The sheaths shall not become brittle or soften over the anticipated exposure temperature and service life of the structure. The minimum wall thickness of sheaths for non-corrosive conditions shall be 0.04 in (1 mm). The sheathing shall have an inside diameter at least 0.030 in (0.76 mm) greater than the maximum diameter of the strand.

Tendons shall be lubricated and protected against corrosion by a properly applied coating of grease or other approved material. Minimum weight of coating material on the prestressing strand shall be not less than 2.5 pounds (1.1 kg) of coating material per 100 ft. (30.5 m) of 0.5 in. (12 mm) diameter strand, and 3.0 pounds (1.4 g) of coating material per 100 ft. (30.5 m) of 0.6 in (15.24 mm) diameter strand. The amount of coating material used shall be sufficient to ensure essentially complete filling of the annular space between the strand and the sheathing. The coating shall extend over the entire tendon length. Coatings shall remain ductile and free from cracks at the lowest anticipated temperature and shall not flow out from the sheath at the maximum anticipated temperature. Coatings shall be chemically stable and non-reactive to the tendon, the concrete and the sheath.

 
1.13.4 Grout  
  Grout for bonded tendons shall consist of a mixture of cement and water unless the gross inside cross-sectional area of the sheath exceeds four times the tendon cross-sectional area, in which case a fine aggregate may be added to the mixture. Fly ash and pozzolanic mineral admixtures may be added at a ratio not to exceed 0.30 by weight of cement. Mineral admixtures shall conform to ASTM C618. Approved shrinkage-compensating material, which is well dispersed through the other admixture, may be used to obtain 5 to 10 percent unrestrained expansion of the grout. Admixtures containing more than trace amounts of chlorides, fluorides, zinc or nitrates shall not be used. Fine aggregate, if used, shall conform to ASTM C404, Size No. 2, except that all material shall pass the No. 16 sieve. Grout shall achieve a minimum compressive strength of 2,500 p.s.i. (17.2 MPa) at 7 days and 5,000 p.s.i. (34.5 MPa) at 28 days when tested in accordance with ASTM C1107, and have a consistency that will facilitate placement. Water content shall be the minimum necessary for proper placement, and the water-cementitious materials ratio shall not exceed 0.45 by weight.  
 
AASHTO T106 (ASTM C109) -- Compressive Strength of Hydraulic Cement Mortar
ASTM C1107 -- Packaged Dry Hydraulic Cement Grout
1.14 Steel Assemblies
  Random sampling shall be done for each production lot of assemblies. Any failure of the visual inspection or bend test shall require like testing on a random 10 percent sample of the production lot. Any failure within this 10 percent sample shall require inspection and bend testing of 100 percent of the production lot, or replacement of the entire lot.

Substitution of reinforcing bars for deformed bar anchors shall not be allowed unless approved by the engineer. 

Weld size and location shall be checked for welded assemblies at a rate of one per 50 assemblies. If discrepancies are found, then all assemblies shall be checked.

 
1.14.1 Stud Anchors  
  Headed stud and deformed bar anchor materials and base metal materials shall be compatible with the stud welding process. Suppliers of both materials shall provide physical and chemical certification on the products supplied. The tests shall correlate to the material supplied. One unit for each 50 assemblies received shall be selected and the stud weld(s) visually inspected, and one stud bend tested, in accordance with the following procedures.  
  The stud-welding operator shall be responsible for the following tests and inspections to ensure that the proper setup variables are being used for the weld position, stud diameter, and stud style being welded. Testing is required for the first two studs in each day's production and any change in the setup such as changing of any one of the following: stud gun, stud welding equipment, stud diameter, gun lift and plunge, total welding lead length, or changes greater than 5 percent in current (amperage) and dwell time.

Down-Hand Stud Welding Qualifications

For studs welded in the down-hand position, at the start of each production period, the operator shall weld two studs of each size and type to a production weld plate or a piece of material similar in material composition to the weld plate and within "25 percent of the production weld plate thickness. The test weld plate and production weld plate pieces shall be clean of any dirt, paint, galvanizing, heavy rust, or other coatings that could prevent successful welding or adversely affect weld quality. These studs shall be visually inspected by the operator to see whether a proper weld fillet has formed. The weld fillet (flash) may be irregular in height or width, but shall completely Awet@ the stud circumference without any visual sign of weld undercut. 

The test studs shall exhibit an after weld length measurement shorter than the before weld stud length. After weld length shall be consistent on both test welds and on all production welds. Typical length reductions for various stud diameters are as follows:
 

Stud Diameter, in. (mm) Length Reduction, in. (mm)
3/16 (5) through 1/2 (12) 1/8 (3)
5/8 (16) through 7/8 (22) 3/16 (5)
1 (25) and over 3/16 to 1/4 (5 to 6)

Records of stud welding shall be maintained on an hourly basis, and be on file at the precast plant.

 
 
AASHTO M102 (ASTM A668) Carbon and Alloy Steel Forgings for General Industrial Use
AASHTO M103 (ASTM A27) Carbon Steel Castings for General Application
AASHTO M111 (ASTM A123) Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
AASHTO M160 (ASTM A6) General Requirements for Rolled Steel Plates, Shapes, Sheet Piling and Bars for Structural Use
AASHTO M164 (ASTM A325) High Strength Bolts for Structural Steel Joints
AASHTO M183 (ASTM A36) Structural Steel
AASHTO M232 (ASTM A153) Zinc Coating (Hot-Dip) on Iron and Steel Hardware
AASHTO M253 (ASTM A490) Heat-Treated Steel Structural Bolts, 150 ksi Minimum Tensile Strength
AASHTO M291 (ASTM A563) Carbon and Alloy Steel Nuts
AASHTO M298 (ASTM B695) Coatings of Zinc Mechanically Deposited on Iron and Steel
AASHTO M299 (ASTM B696) Coatings of Cadmium Mechanically Deposited
AASHTO M300 Inorganic Zinc Rich Primer
AASHTO M314 Steel Anchor Bolts
1.14 Manufactured Hardware and Threaded Inserts  
  Plant tests shall not be required for hardware but certification shall be obtained for all steel materials and each different grade of steel to verify compliance with specifications. Inserts need not be plant tested if used only as recommended by the suppliers and within their stated (certified) capacities and application qualifications. Records shall be on file establishing working capacity of each kind and size of insert used for handling and/or connection corresponding to the actual concrete strengths when inserts are used, unless the manufacturer=s load table indicates adequate capacity at a concrete strength lower than the maximum strength at time of use. No extrapolation of the suppliers test data is permitted. In lieu of certification for hardware, six specimens of each size and material heat number of a steel item shall be tested in accordance with ASTM A370 to verify conformance with the applicable ASTM specification. For other hardware items information shall be on file at the plant describing the material, and its qualities and applications, including limitations.  
1.15 Bearings  
     
1.15.1 Elastomeric Pads  
     
1.15.2 Assemblies  
     
1.16 Grout and Mortar  
     
1.17 Epoxy  
 
AASHTO M200
Epoxy Protective Coatings
1.17.1 Epoxy Mortar  
     
1.17.2 Epoxy for Crack Repair  
     
 
AASHTO M235 (ASTM C881)
Epoxy Resin Adhesives
1.18 Curing Compound  
 
AASHTO M148 (ASTM C309)
Liquid Membrane-Forming Compounds for Curing Concrete
2 CONCRETE  
     
2.1 W/CM Ratio  
  Maximum water-cementitious materials ratio (w/cm) shall be 0.40 by weight.  
2.2 Minimum Cementitious Materials Content  
  Minimum cement content shall be 564 pounds per cubic yard.

When mineral admixtures are used, the minimum total cementitious materials content shall be 611 pounds per cubic yard.

 
2.3 Strength  
  Minimum 28-day design concrete strength shall be 6000 psi.

The age for determining design strength (f=c) may be increased at the discretion of the Engineer.

At the Engineer's discretion, concrete strength up to 8,000 psi at 28 days may be specified.
2.3.1 Prestress Transfer Strength  
  The minimum concrete strength at transfer of prestressing force shall be 4000 psi or as determined by the following relationships, whichever is greater.
  • where f'ci is the required strength at transfer (psi) and fc is the maximum compressive stress at transfer (psi), or
  • where ft' is the maximum tensile stress at transfer (psi) between the end of the member and the transfer point, or
  • where ft is the maximum tensile stress at transfer (psi) except as defined by b) above.
Where the concrete strength at transfer of prestressing force is controlled by tensile stresses, supplemental tensile reinforcement may be provided to control the stress. In this case, reinforcement shall resist the total tensile force and the transfer strength determined by the maximum allowable compressive stress.
 
2.4 Proportioning  
  Concrete mix proportions shall be established under carefully controlled laboratory conditions. For concrete mixes, representative cylinders shall be cast and cured under plant production conditions to demonstrate the strength and weight of the concrete produced. All concrete mixes shall be developed using the brand and type of cement, the type and gradation of aggregates, and the type of admixtures proposed for use in production mixes. If at any time these variables are changed, the mix shall be reevaluated. This reevaluation may include one or more of the following concrete properties: (1) air content or durability, and (2) strength (selected tests at appropriate ages).  
2.5 Mixing  
     
2.6 Delivery  
     
2.7 Placement  
     
2.8 Consolidation  
     
2.9 Sampling  
     
2.10 Testing  
  Records of all concrete mixes used in a plant and their respective test results shall be on file. 

b. Samples for testing shall be obtained in accordance with AASHTO T141. 

 
2.10.1 Compression   
  In addition to the 28-day tests, compression tests shall be made at the time of stripping the production unit from the mold to determine whether stripping strength requirements have been met.  
2.10.1.1 Specimens  
  Standard test specimens shall be 6 x 12-inch 150 x 300-mm or 4 x 8-inch 100 x 200-mm cylinders.  
2.10.1.2 Handling & Curing  
  Test specimens shall be made and cured in accordance with AASHTO T126.  
2.10.1.3 Procedure  
  Specimens shall be tested in accordance with AASHTO T22. Test specimens using 4-inch 100-mm cylinders are permitted providing proper correlation data with the standard 6 x 12-inch 150 x 300-mm test cylinder is available.  
2.10.2 Slump  
  Slump tests shall be conducted in accordance with AASHTO T119. Tests shall be made on the first concrete delivery, whenever compressive test specimens are made, and whenever the consistency of the concrete appears to change significantly.  
2.10.3 Air Content  
  Air content shall be measured in accordance with ASTM C173 or C231 as applicable. Tests shall be made on the first concrete delivery and whenever compressive test specimens are made.  
2.10.4 Unit Weight  
  Unit weight shall be tested in accordance with AASHTO T121 or ASTM C567. Unit weight of normal weight concrete shall be tested once per week for each mix design in use. Lightweight concrete shall be tested daily to confirm batching consistency. 

When the nominal fresh unit weight varies from the design value by more than _2 pcf _32 kg/m3 for normal weight concrete or _2 percent for structural lightweight concrete, batch adjustments shall be made.

 
2.10.5 Temperature  
  Temperature shall be tested in accordance with ASTM C1064. Test shall be conducted whenever slump, air content tests or compressive test specimens are made. AASHTO M205 (ASTM C470) Molds for Forming Concrete Test Cylinders Vertically
AASHTO T22 (ASTM C39) Compressive Strength of Cylindrical Concrete Specimens
AASHTO T23 (ASTM C31) Making and Curing Concrete Test Specimens in the Field
AASHTO T119 (ASTM C143) Slump of Hydraulic Cement Concrete
AASHTO T121 (ASTM C138) Mass per Cubic Foot, Yield, and Air Content (Gravimetric) of Concrete
AASHTO T126 (ASTM C192) Making and Curing Concrete Test Specimens in the Laboratory
AASHTO T141 (ASTM C172) Sampling Freshly Mixed Concrete
AASHTO T152 (ASTM C231) Air Content of Freshly Mixed Concrete by the Pressure Method
AASHTO T196 (ASTM C173) Air Content of Freshly Mixed Concrete by the Volumetric Method
ASTM C1064 Temperature of Freshly Mixed Portland Cement Concrete
2.11 Curing  
2.11.1 Standard  
2.11.2 Accelerated  
2.11.2.1 Moisture Retention  
2.11.2.2 Temperature Limits  
2.11.2.3 Initial Set  
3 PROCESSES  
3.1 Placement of Reinforcement  
3.1.1 Fastening  
3.2 Tensioning  
3.2.1 Equipment  
3.2.2 Initial  
3.2.3 Final  
3.2.3.1 Straight  
3.2.3.2 Harped  
3.2.4 De-Tensioning  
3.2.5 Post-Tensioning  
3.3 Forming  
3.4 Finishing  
3.5 Form Removal  
3.6 Handling  
3.7 Storage  
4 PLANT  
4.1 Certification  
5 PERSONNEL  
5.1 Training/Certification  
6 TOLERANCES  
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